Australian experts react to Mediterranean Diet research findings

Australian medical and nutrition experts have reacted differently to the research findings of a study published December 2014 in the British Medical Journal. The study showed the Mediterranean diet appears to be associated with longer telomere length – an established marker of slower ageing.

According to the study by US researchers from Brigham and Women’s Hospital and Harvard Medical School, eating a Mediterranean diet might help extend your lifespan.

The Mediterranean diet is characterised by a high intake of vegetables, fruits, nuts, legumes (such as peas, beans and lentils), and (mainly unrefined) grains; a high intake of olive oil but a low intake of saturated fats; a moderately high intake of fish, a low intake of dairy products, meat and poultry; and regular but moderate intake of alcohol (specifically wine with meals).

Australian medical dietary expert warns study does not prove causation

Professor Vlado Perkovic, Executive Director of The George Institute for Global Health and a Professor of Medicine at The University of Sydney, warned that the study does not prove causation and caution should be used.

Professor Perkovic said people eating a Mediterranean diet have been known to have reduced rates of vascular diseases like heart attack and that “a number of studies have suggested it may be a method of preventing cardiovascular events and other poor outcomes”.

“The mechanism by which any benefit might occur is unknown,” Professor Perkovic said. “The present paper shows a relationship between adherence to the Mediterranean diet and telomere length, a marker that has been linked to longevity. It is proposed that benefits of the Mediterranean diet on outcomes might occur through this mechanism,” he said.

However he said the data needed to be “prospectively assessed to be more robust” and take into account factors such as participants who followed the diet also being less likely to smoke and more likely to be physically active. He said it was also “not clear which aspects of the diet might be important”.

“Having said that, the results highlight the importance of diet in driving length and quality of life, and suggest that following a sensible healthy diet, many aspects of which are part of what is described as a Mediterranean diet, is likely to improve health for all Australians,” Professor Perkovic said.

Australian nutritionist welcomes findings

Dr Rosemary Stanton, a nutritionist and a Visiting Fellow at the School of Medical Sciences at the University of New South Wales, said the study added to existing knowledge and “supports the messages of Australia’s Dietary Guidelines”.

“This latest study adds to the long line of evidence showing that adherence to the Mediterranean diet is linked to lower all-cause mortality, reduced incidence of major cardiovascular diseases and other chronic diseases, and greater health and well-being in people who survive to older ages,” Dr Stanton said. “This particular study had a large number of participants and corrected the data for confounding factors,” she said.

“It also shows the futility (when looking at associations between diet and health) of looking at individual nutrients and the wisdom of assessing the whole dietary pattern,” Dr Stanton said.

Dr Stanton said the Mediterranean diet was not the only dietary pattern associated with health and longevity, but it was the “most studied”.

Telomeres prolong life

The study found that the Mediterranean diet was associated with increased telomere length. Telomeres sit on the end of chromosomes (like the plastic tips on the end of shoelaces), stopping them from fraying and scrambling the genetic codes they contain. In healthy people, telomeres shorten progressively throughout life, more than halving in length from infancy to adulthood, and halving again in the very elderly.

Shorter telomeres are thus associated with lower life expectancy and greater risk of age-related diseases. Lifestyle factors, such as obesity, cigarette smoking, and consumption of sugar sweetened drinks, have all been linked to people having shorter telomeres than typically occur in people of a similar age. Oxidative stress and inflammation have also been shown to speed up telomere shortening.

Study method

Given that fruits, vegetables, and nuts – key components of the Mediterranean diet – have well known antioxidant and anti-inflammatory effects, a team of US researchers, led by Immaculata De Vivo, Associate Professor at Brigham and Women’s Hospital and Harvard Medical School, set out to examine whether adherence to the Mediterranean diet was associated with longer telomere length.

They analysed data on 4,676 healthy middle-aged women from the Nurses’ Health Study – an ongoing study tracking the health of more than 120,000 US nurses since 1976. Participants completed detailed food questionnaires and had a blood test to measure telomere length.

A diet score ranging from 0-9 points was calculated for each participant, with a higher score representing a closer resemblance to the Mediterranean diet.

After adjusting for other potentially influential factors, the results show that greater adherence to the Mediterranean diet was significantly associated with longer telomeres. Each one point change in diet score corresponded on average to 1.5 years of telomere ageing.

Overall diet more important than dietary components, researchers

However, none of the individual dietary components was associated with telomere length, underlining the importance of examining dietary patterns in relation to health, not just separate dietary factors such as intake of whole grains, say the authors.

“To our knowledge, this is the largest population-based study specifically addressing the association between Mediterranean diet adherence and telomere length in healthy, middle-aged women,” the researchers wrote. “Our results further support the benefits of adherence to the Mediterranean diet for promoting health and longevity,” they said.

A Mediterranean diet is the “cornerstone of dietary advice” in cardiovascular disease prevention, and the fact that it also links with a biomarker of slower ageing is “reassuring”, according to Professor Peter Nilsson from Lund University, Sweden in an accompanying editorial. He suggests that genetic background factors, reflecting ancestry, could probably explain some of the variation in the association between dietary patterns and telomere length, and that future studies on this question “should take into account the possibility of interactions between genes, diet, and sex.”